JP2011022281A - Semiconductor device and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor device capable of suppressing an embedding part embedding a mesa structure from peeling off from a mesa structure part, and to provide a method for manufacturing the semiconductor device. <P>SOLUTION: The semiconductor device includes an optical semiconductor element provided with the mesa structure part 21, the embedding part 22 embedding the mesa structure part 21 from at least the lateral side thereof, and an electrode 23 connected to the mesa structure part 21. A first organic insulating film 8 formed on the lateral side of the mesa structure part 21, a second organic insulating film 11 formed to be made away from the mesa structure part 21 more than the first organic insulating film 8 and an inorganic insulating film 10 formed between the first and second organic insulating films 8 and 11 are provided in the embedding part 22. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a semiconductor device and a manufacturing method thereof.

  In recent years, optical waveguides (including optical modulators) with high-mesa or ridge-structure mesa structures are formed by spin coating for the purpose of improving operating speed, high integration, multiple functions, and low cost. Studies have been conducted on a structure in which a mesa structure is embedded by an organic insulating film that can be used. According to the spin coating method, the organic insulating film can be formed with good coverage. For this reason, it is suitable for cost reduction and shortening of manufacturing time. In addition, since the dielectric constant of the organic insulator is lower than that of a semiconductor, it is suitable for reducing the parasitic capacitance and improving the operation speed in an active device such as an optical modulator having electrodes. In addition, since the refractive index of the organic insulator is lower than that of the semiconductor, both the active device and the passive device having no electrode are suitable for miniaturization and high performance by the high refractive index contrast. Furthermore, a high light confinement effect can be obtained in both the active device and the passive device.

  The width of the optical waveguide through which light can propagate in a single mode is about 1 μm, and the width of the mesa structure is conventionally about 1 μm. For this reason, when the periphery of the mesa structure portion is a space, it is difficult to form the electrode of the active device on the mesa structure portion. For this reason, the organic insulating film is also used as an electrode stage. In other words, when the active device is manufactured, the electrode is formed after the organic insulating film is formed.

  However, the organic insulating film may be peeled off from the mesa structure during electrode formation. FIG. 1 is a cross-sectional view showing peeling of an organic insulating film that may occur when an element is manufactured by using a conventional method for manufacturing a semiconductor device, and damage to an electrode.

  Conventionally, as shown in FIG. 1, a mesa structure including an n-type cladding layer 102, a core layer 103, a p-type cladding layer 104, and a p-type contact layer 105 is formed on an n-type semiconductor substrate 101. Thereafter, an organic insulating film 108 for embedding the mesa structure portion is formed. Thereafter, the electrode 115 is formed on the mesa structure portion using the organic insulating film 108 as a stage. However, the organic insulating film 108 tends to shrink during the plasma treatment and heat treatment required for forming the electrode 115. For this reason, as shown in FIG. 1, the organic insulating film 108 may be peeled off from the mesa structure. When such peeling occurs, it is difficult to form the electrode 115. Even if the organic insulating film 108 does not peel off during manufacturing, the organic insulating film 108 may be peeled off due to the influence of heat generated during operation, and the electrode 115 may peel off accordingly.

  Such peeling occurs not only in an optical waveguide having a mesa structure portion having a high mesa structure but also in an optical waveguide having a mesa structure portion having a ridge structure. It also occurs in semiconductor lasers having mesa structures as well as optical waveguides.

JP 2004-280018 A JP 2004-128360 A

  An object of the present invention is to provide a semiconductor device and a method for manufacturing the same, which can suppress peeling of a buried portion embedding a mesa structure from the mesa structure portion.

  In one aspect of the semiconductor device, an optical semiconductor element including a mesa structure portion, an embedded portion in which the mesa structure portion is embedded at least from the side, and an electrode connected to the mesa structure portion are provided. The buried portion includes a first organic insulating film formed on a side of the mesa structure portion and a second organic insulating film formed farther from the mesa structure portion than the first organic insulating film. A film and an inorganic insulating film formed between the first organic insulating film and the second organic insulating film are provided.

  In one aspect of a method for manufacturing a semiconductor device, an optical semiconductor element including a mesa structure is formed, an embedded portion that embeds the mesa structure from at least a side is formed, and an electrode connected to the mesa structure is formed To do. When forming the buried portion, a first organic insulating film is formed on the side of the mesa structure portion, and a second organic insulating film that is separated from the mesa structure portion is formed with respect to the first organic insulating film. And forming an inorganic insulating film between the first organic insulating film and the second organic insulating film.

  According to the semiconductor device or the like, even if the second organic insulating film is thermally deformed, the deformation of the first organic insulating film is suppressed by the inorganic insulating film. For this reason, peeling of the 1st organic insulating film from a mesa structure part can be suppressed.

It is sectional drawing which shows peeling of the organic insulating film which may generate | occur | produce when an element is produced using the manufacturing method of the conventional semiconductor device, and the damage of the electrode by it. It is sectional drawing which shows the structure of the semiconductor device which concerns on 1st Embodiment. It is sectional drawing which shows the method of manufacturing the semiconductor device which concerns on 1st Embodiment in order of a process. FIG. 3B is a cross-sectional view illustrating a method of manufacturing the semiconductor device in order of processes subsequent to FIG. 3A. FIG. 3B is a cross-sectional view illustrating a method of manufacturing the semiconductor device in order of processes subsequent to FIG. 3B. FIG. 3D is a cross-sectional view illustrating the method of manufacturing the semiconductor device in order of processes subsequent to FIG. 3C. FIG. 3D is a cross-sectional view illustrating a method of manufacturing the semiconductor device in order of processes subsequent to FIG. 3D. FIG. 3E is a cross-sectional view illustrating a method for manufacturing the semiconductor device in order of process, following FIG. 3E. It is sectional drawing which shows the structure of the semiconductor device which concerns on 2nd Embodiment. It is sectional drawing which shows the method of manufacturing the semiconductor device which concerns on 2nd Embodiment to process order. It is a layout figure which shows the structure of the MZ modulator which concerns on 3rd Embodiment. It is sectional drawing which shows the structure of the MZ modulator which concerns on 3rd Embodiment. It is sectional drawing which shows the structure of the semiconductor device which concerns on 4th Embodiment. It is sectional drawing which shows the structure of the semiconductor device which concerns on 5th Embodiment.

  Hereinafter, embodiments of the present invention will be specifically described with reference to the accompanying drawings.

(First embodiment)
First, the first embodiment will be described. FIG. 2 is a cross-sectional view showing the structure of the semiconductor device according to the first embodiment.

  As shown in FIG. 2, in the semiconductor device according to the first embodiment, a mesa structure portion 21 having a high mesa structure is formed on an n-type n-InP substrate 1. The width of the mesa structure portion 21 is about 1.0 μm to 2.0 μm (for example, 1.4 μm). In the mesa structure portion 21, an n-type n-InP clad layer 2, an intrinsic i-InGaAsP core layer 3, a p-type p-InP clad layer 4 and a p-type p-InGaAs contact layer 5 are sequentially stacked. It is included. The n-InP cladding layer 2 has a thickness of about 50 nm to 500 nm (for example, 300 nm). The i-InGaAsP core layer 3 has a thickness of about 150 nm to 400 nm (for example, 230 nm) and a composition wavelength of about 1.2 μm to 1.4 μm (for example, 1.3 μm). The thickness of the p-InP cladding layer 4 is about 0.5 μm to 2.0 μm (for example, 1 μm). The thickness of the p-InGaAs contact layer 5 is about 100 nm to 400 nm (for example, 300 nm).

  The mesa structure portion 21 is embedded by the embedded portion 22. The buried portion 22 includes a silicon oxide film 7, an organic insulating film 8, a silicon nitride film 10, and an organic insulating film 11. The silicon oxide film 7 directly covers the side surface of the mesa structure 21 and the surface of the n-InP substrate 1. The thickness of the silicon oxide film 7 is about 200 nm to 600 nm (for example, 400 nm). The organic insulating film 8 is formed on both sides of the mesa structure portion 21 so as to be in contact with the portion of the silicon oxide film 7 that is in contact with the side surface of the mesa structure portion 21. That is, a part of the silicon oxide film 7 is sandwiched between the mesa structure portion 21 and the organic insulating film 8. The width of the organic insulating film 8 is about 2.0 μm to 8.0 μm (for example, 4.3 μm). The silicon nitride film 10 covers the upper and side surfaces of the organic insulating film 8 and the portion of the silicon oxide film 7 exposed from the organic insulating film 8. That is, the organic insulating film 8 is sandwiched between the silicon oxide film 7 and the silicon nitride film 10 in a direction parallel to the surface of the n-InP substrate 1. The thickness of the silicon nitride film 10 is about 200 nm to 500 nm (for example, 300 nm). The organic insulating film 11 is formed on both sides of the mesa structure portion 21 so as to be in contact with the portion of the silicon nitride film 10 that is in contact with the side surface of the organic insulating film 8. That is, a part of the silicon nitride film 10 is sandwiched between the organic insulating films 8 and 11. The organic insulating films 8 and 11 contain, for example, benzocyclobutene (BCB) as a main raw material.

  Further, a silicon nitride film 12 covering the silicon nitride film 10 and the organic insulating film 11 is formed. The thickness of the silicon nitride film 12 is about 200 nm to 500 nm (for example, 300 nm). In the silicon nitride films 12 and 10, an opening 14 exposing a part of the organic insulating film 8 and the p-InGaAs contact layer 5 is formed, and an electrode 23 is formed in the opening 14. The electrode 23 includes a conductive film 15, a conductive film 16, and an Au film 18. The conductive film 15 includes, for example, an Au film, a Zn film, and an Au film that are sequentially stacked. The conductive film 16 includes, for example, a Ti film, a Pt film, and an Au film that are sequentially formed.

  An Au film 20 is formed on the back surface of the n-InP substrate 1 with a conductive film 19 interposed therebetween.

  The amount of deformation in a certain direction of the object increases as the dimension in the direction increases. Therefore, in the conventional semiconductor device shown in FIG. 1, the amount of deformation in the direction away from the mesa structure portion of the organic insulating film 108 increases as the dimension in this direction increases. On the other hand, in this embodiment, the silicon nitride film 10 is interposed between the organic insulating film 8 and the organic insulating film 11 that also function as the stage of the electrode 23. The silicon nitride film 10 has an extremely low thermal deformation rate as compared with the organic insulating film 8. For this reason, the amount of deformation of the organic insulating film 8 in the direction away from the mesa structure portion 21 is reduced by the silicon nitride film 10. That is, the silicon nitride film 10 suppresses deformation of the organic insulating film 8 due to thermal deformation of the organic insulating film 11. Therefore, peeling of the organic insulating film 8 during formation of the electrode 23 and peeling of the organic insulating film 8 due to heat generation during operation are less likely to occur. Even if the organic insulating film 11 is peeled off from the silicon nitride film 10, the electrode 23 is hardly peeled off by this.

  In the present embodiment, the silicon nitride film 10 has a portion that extends parallel to the side surface of the mesa structure portion 21 and completely divides the organic insulating films 8 and 11, but the organic insulating films 8 and 11 are completely divided from each other. There is no need to be. That is, in order to effectively suppress the influence of thermal deformation of the organic insulating film 11, it is desirable that the organic insulating film 8 is completely divided, but a part of the organic insulating film 8 is related to the manufacturing process and the like. And a part of the organic insulating film 11 may be in contact with each other.

  Next, a method for manufacturing the semiconductor device according to the first embodiment will be described. 3A to 3F are cross-sectional views illustrating a method of manufacturing the semiconductor device according to the first embodiment in the order of steps.

  First, as shown in FIG. 3A (a), an n-InP clad layer 2, an i-InGaAsP core layer 3, a p-InP clad layer 4 and a p-InGaAs contact layer 5 are arranged in this order on an n-InP substrate 1. Form with. In forming the n-InP clad layer 2, the i-InGaAsP core layer 3, the p-InP clad layer 4, and the p-InGaAs contact layer 5, these are epitaxially grown by, for example, metal organic chemical vapor deposition (MOCVD). Next, a hard mask 6 is formed on the p-InGaAs contact layer 5. In forming the hard mask 6, for example, a silicon oxide film is formed on the entire surface of the p-InGaAs contact layer 5, and this silicon oxide film is patterned using photolithography or the like. The width of the hard mask 6 is approximately the same as the width of the mesa structure portion 21 to be formed later (for example, 1.4 μm).

  Thereafter, as shown in FIG. 3A (b), the p-InGaAs contact layer 5, the p-InP cladding layer 4, the i-InGaAsP core layer 3, and the n-InP cladding layer 2 are etched using the hard mask 6 as a mask. Thus, the mesa structure portion 21 having a height of about 3 μm is formed. As the etching of the p-InGaAs contact layer 5, the p-InP cladding layer 4, the i-InGaAsP core layer 3, and the n-InP cladding layer 2, for example, inductively coupled reactive ion etching (ICP-RIE) is performed.

  Subsequently, as shown in FIG. 3A (c), the hard mask 6 is removed. Next, the silicon oxide film 7 is formed by, for example, a chemical vapor deposition (CVD) method or the like. Thereafter, an organic insulating film 8 is formed on the silicon oxide film 7. The thickness of the organic insulating film 8 is made larger than the height of the mesa structure portion 21. In forming the organic insulating film 8, a solution such as BCB, for example, is applied onto the silicon oxide film 7 by spin coating or the like, and then fixed by performing heat treatment (cure) under appropriate conditions.

Next, as shown in FIG. 3B (d), the organic insulating film 8 is dry-etched so that the surface of the organic insulating film 8 is substantially aligned with the surface of the p-InGaAs contact layer 5. As a result, the portion of the silicon oxide film 7 on the p-InGaAs contact layer 5 protrudes from the surface of the organic insulating film 8. As the dry etching of the organic insulating film 8, for example, RIE using a mixed gas of O ₂ gas and CF ₄ gas (O ₂ gas flow rate: CF ₄ gas flow rate = 4: 1) is performed.

  Thereafter, as shown in FIG. 3B (e), the portion of the silicon oxide film 7 protruding from the surface of the organic insulating film 8 is removed by etching, and the surface of the p-InGaAs contact layer 5 is exposed. As this etching, either wet etching or dry etching may be performed.

  Subsequently, as shown in FIG. 3B (f), a hard mask 9 is formed on the mesa structure portion 21 and the organic insulating film 8. In the formation of the hard mask 9, for example, a silicon nitride film is formed on the mesa structure portion 21 and the organic insulating film 8, and this silicon nitride film is patterned using photolithography or the like. The width of the hard mask 9 is approximately the same as the sum of the width of the mesa structure portion 21 and the width of the organic insulating film 8 to be left later (for example, 10 μm).

Next, as shown in FIG. 3C (g), the organic insulating film 8 is etched using the hard mask 9 as a mask until the silicon oxide film 7 is exposed. As the etching of the organic insulating film 8, for example, RIE using a mixed gas of O ₂ gas and CF ₄ gas (O ₂ gas flow rate: CF ₄ gas flow rate = 4: 1) is performed.

  Thereafter, as shown in FIG. 3C (h), the hard mask 9 is removed. Subsequently, the silicon nitride film 10 is formed by, for example, a CVD method. Next, an organic insulating film 11 is formed on the silicon nitride film 10. The thickness of the organic insulating film 11 is made larger than the height of the mesa structure portion 21. In the formation of the organic insulating film 11, for example, the same processing as the formation of the organic insulating film 8 is performed.

Thereafter, as shown in FIG. 3C (i), the organic insulating film 11 is etched until the silicon nitride film 10 is exposed. As the etching of the organic insulating film 11, for example, RIE using a mixed gas of O ₂ gas and CF ₄ gas (O ₂ gas flow rate: CF ₄ gas flow rate = 4: 1) is performed. Subsequently, a silicon nitride film 12 is formed on the silicon nitride film 10 and the organic insulating film 11.

  Next, as shown in FIG. 3D (j), a resist pattern 13 having an opening for opening a region where an electrode 23 is to be formed is formed on the silicon nitride film 12. As the resist pattern 13, for example, a multi-layered structure and a saddle structure are formed. Then, the silicon nitride films 12 and 10 are wet-etched using the resist pattern 13 as a mask, thereby forming an opening 14 exposing the p-InGaAs contact layer 5.

  Thereafter, as shown in FIG. 3D (k), the conductive film 15 is formed with the resist pattern 13 remaining. In the formation of the conductive film 15, for example, an Au film, a Zn film, and an Au film are deposited in this order. The conductive film 15 is formed from the p-InGaAs contact layer 5 to the organic insulating film 8, and is also formed on the resist pattern 13.

  Subsequently, as shown in FIG. 3D (l), the resist pattern 13 is removed together with the conductive film 15 formed thereon. As a result, the conductive film 15 remains only in the opening 14. That is, lift-off processing is performed.

  Next, as shown in FIG. 3E (m), a conductive film 16 is formed on the entire surface by sputtering or the like. In forming the conductive film 16, for example, a Ti film, a Pt film, and an Au film are deposited in this order.

  Thereafter, as shown in FIG. 3E (n), a resist pattern 17 having an opening for opening a region where the electrode 23 is to be formed is formed. Then, an Au film 18 is formed in the opening of the resist pattern 17 by a plating method using the conductive film 16 as a plating electrode.

  Subsequently, as shown in FIG. 3E (o), the resist pattern 17 is removed. Further, the conductive film 16 exposed from the Au film 18 is removed by dry etching using the Au film 18 as a mask. In this way, the surface-side electrode 23 is formed.

  Next, as shown in FIG. 3F (p), the back surface of the n-InP substrate 1 is polished so that the thickness of the n-InP substrate 1 is about 150 μm. Thereafter, a conductive film 19 is formed on the entire back surface of the n-InP substrate 1. In the formation of the conductive film 19, for example, an AuGe film and an Au film are deposited in this order, and patterning is performed. Subsequently, an Au film 20 is formed on the conductive film 19 by a plating method using the conductive film 19 as a plating electrode. In this way, the back side electrode is formed.

  Thereafter, by performing heat treatment, the p-InGaAs contact layer 5 and the conductive film 15 are brought into ohmic contact with each other, and the n-InP substrate 1 and the conductive film 19 are brought into ohmic contact with each other. Further, wiring and the like are formed as necessary to complete the semiconductor device.

(Second Embodiment)
Next, a second embodiment will be described. FIG. 4 is a cross-sectional view showing the structure of the semiconductor device according to the second embodiment.

  As shown in FIG. 4, the organic insulating film 11 is located not only on the side of the organic insulating film 8 but also on the organic insulating film 8 with the silicon nitride film 10 interposed therebetween. That is, the organic insulating film 11 is also in contact with the portion of the silicon nitride film 10 located on the organic insulating film 8. Other configurations are the same as those of the first embodiment.

  The effect similar to 1st Embodiment is acquired also by such 2nd Embodiment. Further, the organic insulating film 11 is less likely to be peeled off from the silicon nitride film 10 as compared with the first embodiment. This is because the portion of the organic insulating film 11 located above the organic insulating film 8 is in close contact with the surface of the silicon nitride film 10, and this portion is resistant to peeling.

  Next, a method for manufacturing the semiconductor device according to the second embodiment will be described. FIG. 5 is a cross-sectional view showing a method of manufacturing the semiconductor device according to the second embodiment in the order of steps.

First, processing up to the formation of the organic insulating film 11 is performed as in the first embodiment (FIG. 3C (h)). Next, as shown in FIG. 5A, the organic insulating film 11 is etched by leaving 0.2 μm to 0.7 μm (for example, 0.5 μm) on the portion of the silicon nitride film 10 located on the organic insulating film 8. To do. As the etching of the organic insulating film 11, for example, RIE using a mixed gas of O ₂ gas and CF ₄ gas (O ₂ gas flow rate: CF ₄ gas flow rate = 4: 1) is performed.

  Thereafter, a silicon nitride film 12 is formed on the organic insulating film 11 as shown in FIG.

  Subsequently, as shown in FIG. 5C, a resist pattern 13 having an opening for opening a region where the electrode 23 is to be formed is formed on the silicon nitride film 12. As the resist pattern 13, for example, a multi-layered structure and a saddle structure are formed. Then, using the resist pattern 13 as a mask, the silicon nitride film 12 is wet etched, the organic insulating film 11 is dry etched, and the silicon nitride film 10 is wet etched to expose the p-InGaAs contact layer 5. 14 is formed.

  Thereafter, similarly to the first embodiment, the processes after the formation of the conductive film 15 are performed to complete the semiconductor device.

(Third embodiment)
Next, a third embodiment will be described. The third embodiment relates to a Mach-Zehnder (MZ) optical modulator including an optical waveguide. FIG. 6 is a layout diagram showing the configuration of the MZ modulator according to the third embodiment. 7A is a cross-sectional view taken along line II in FIG. 6, FIG. 7B is a cross-sectional view taken along line II-II in FIG. 6, and FIG. It is sectional drawing along a III line.

  As illustrated in FIG. 6, the MZ modulator according to the third embodiment includes a demultiplexing unit 41, a phase modulation unit 42, and a multiplexing unit 43 that are arranged in order from the light input side. The demultiplexing unit 41, the phase modulation unit 42, and the multiplexing unit 43 are provided with two optical waveguides 31 penetrating therebetween. The optical waveguide 31 also includes a bent waveguide (curved portion). As shown in FIG. 7, the demultiplexing unit 41, the phase modulation unit 42, and the multiplexing unit 43 are formed using the n-InP substrate 1.

  The demultiplexing unit 41 is provided with a multimode interferometer (MMI) optical multiplexer 32. The MMI optical multiplexer 32 demultiplexes the light guided through one of the two optical waveguides 31 located on the input side, demultiplexes it to the two optical waveguides 31 located on the output side, and outputs the demultiplexed light. .

  The phase modulation unit 42 is provided with a phase modulator including an electrode 33 that applies an electric field that changes the refractive index of the semiconductor layers in the two optical waveguides 31. In this phase modulator, the interference state between the signal lights passing through the two optical waveguides 31 is adjusted according to the change in the refractive index of the semiconductor layer.

  The multiplexer 43 is provided with an MMI optical multiplexer 34. The MMI optical multiplexer 34 multiplexes the light guided through the two optical waveguides 31 positioned on the input side and outputs the multiplexed light to the two optical waveguides 31 positioned on the output side.

  FIG. 7A shows a cross section taken along the line II in the phase modulation section 42. As shown in FIG. 7A, the cross-sectional structure of each optical waveguide 31 is the same as that of the first embodiment, and the electrode 23 in the first embodiment functions as the electrode 33. In addition, the optical waveguide 31 in the phase modulation unit 42 functions as an arm.

  FIG. 7B shows a cross section taken along line II-II in the demultiplexing unit 41. As shown in FIG. 7B, the MMI optical multiplexer 32 is provided with one optical waveguide obtained by integrating two optical waveguides 31 on the input side. In the MMI optical multiplexer 32, the opening 14 and the electrode 23 are not provided, and the widths of the n-InP cladding layer 2, the i-InGaAsP core layer 3, the p-InP cladding layer 4, and the p-InGaAs contact layer 5 are provided. The cross-sectional structure is the same as that shown in the first embodiment except that is wide. An optical waveguide 31 that bisects the optical waveguide of the MMI optical multiplexer 32 is located at the subsequent stage of the MMI optical multiplexer 32. The cross-sectional structure of the MMI optical multiplexer 34 of the multiplexing unit 43 is also the same.

  FIG. 7C shows a cross section taken along the line III-III in the branching section 41. As shown in FIG. 7C, the two optical waveguides 31 on the input side of the MMI optical multiplexer 32 are the same as those shown in the first embodiment except that the opening 14 and the electrode 23 are not provided. It has the same cross-sectional structure.

  Thus, the structure of the first embodiment can be adopted to configure the MZ modulator. You may employ | adopt the structure of 2nd Embodiment.

  Further, the pattern of the hard mask 6 may be adjusted to adjust the layout of the optical waveguide 31 including the bent waveguide, and the pattern of the resist pattern 13 may be adjusted to adjust the layout of the electrode 33. In parallel with the formation of the phase modulation unit 42 which is an active device, the upper and lower surfaces of the entire semiconductor device are formed by forming the input / output optical waveguide 31, the MMI optical multiplexers 32 and 34 which are passive devices, the bent waveguide and the like. Can be ensured.

  Note that a phase adjustment region may be provided as necessary, and the same structure as that of the first or second embodiment may be adopted for the organic insulating film and the electrode in the phase adjustment region. Further, a structure similar to that of the first or second embodiment may be adopted around the electrode in the light absorption region of an electro-absorption (EA) modulator. In this case, an electrode may be used to apply an electric field that changes the absorption coefficient of the semiconductor layer constituting the optical waveguide.

(Fourth embodiment)
Next, a fourth embodiment will be described. FIG. 8 is a cross-sectional view showing the structure of the semiconductor device according to the fourth embodiment.

  Whereas the mesa structure portion 21 of the first embodiment has a high mesa structure, the mesa structure portion 24 having a ridge structure is provided in the fourth embodiment. That is, the n-InP clad layer 2 and the i-InGaAsP core layer 3 are formed on the n-InP substrate 1, and the mesa structure portion 24 having the ridge structure is provided thereon. The mesa structure 24 includes a p-InP cladding layer 4 and a p-InGaAs contact layer 5. The mesa structure portion 24 is embedded by the embedded portion 22. Other configurations are the same as those of the first embodiment.

  According to the fourth embodiment as described above, the same effect as that of the first embodiment can be obtained. Then, according to the required characteristics, the first embodiment employing the high mesa structure and the fourth embodiment employing the ridge structure can be selected. In the second embodiment, a ridge structure may be adopted.

(Fifth embodiment)
Next, a fifth embodiment will be described. The first to fourth embodiments relate to the optical waveguide, while the fifth embodiment relates to the semiconductor laser. FIG. 9 is a cross-sectional view showing the structure of the semiconductor device according to the fifth embodiment.

  As shown in FIG. 9, in the semiconductor device according to the fifth embodiment, a cladding layer 52 and an active layer 53 are formed on a substrate 51. A mesa structure 74 having a ridge structure is formed on the active layer 53. The mesa structure 74 includes a cladding layer 54 and a contact layer 55.

  The mesa structure portion 74 is embedded by the embedded portion 72. The buried portion 72 includes a silicon oxide film 57, an organic insulating film 58, a silicon nitride film 60 and an organic insulating film 61. The silicon oxide film 57 directly covers the side surface of the mesa structure 74 and the surface of the cladding layer 54. The organic insulating film 58 is formed on both sides of the mesa structure portion 74 so as to be in contact with the portion of the silicon oxide film 57 that is in contact with the side surface of the mesa structure portion 74. That is, a part of the silicon oxide film 57 is sandwiched between the mesa structure portion 74 and the organic insulating film 58. The silicon nitride film 60 covers the upper and side surfaces of the organic insulating film 58 and the portion of the silicon oxide film 57 exposed from the organic insulating film 58. That is, the organic insulating film 58 is sandwiched between the silicon oxide film 57 and the silicon nitride film 60 in a direction parallel to the surface of the substrate 51. The organic insulating film 61 is formed on both sides of the mesa structure portion 74 so as to be in contact with the portion of the silicon nitride film 60 that is in contact with the side surface of the organic insulating film 58. That is, a part of the silicon nitride film 60 is sandwiched between the organic insulating films 58 and 61. The organic insulating films 58 and 61 contain, for example, BCB as a main material.

  Further, a silicon nitride film 62 covering the silicon nitride film 60 and the organic insulating film 61 is formed. In the silicon nitride films 62 and 60, an opening 64 that exposes part of the organic insulating film 58 and the contact layer 55 is formed, and an electrode 65 is formed in the opening 64.

  An electrode 66 is formed on the back surface of the substrate 51.

  Even in such a semiconductor laser as in the fifth embodiment, the same effects as in the first embodiment can be obtained. In particular, the semiconductor laser is suitable in terms of reduction of parasitic capacitance and improvement of surface flatness.

  In any of the embodiments, the material is not particularly limited. For example, another compound semiconductor may be used instead of the InP-based semiconductor. Further, the composition wavelength of the core layer or the like is not limited to the above. Further, the materials of the inorganic insulating film and the organic insulating film are not limited to silicon oxide, silicon nitride, and BCB. Further, the material of the electrode is not limited to the above. The formation method and thickness of each film are not limited to those described above.

  Hereinafter, various aspects of the present invention will be collectively described as supplementary notes.

(Appendix 1)
An optical semiconductor element having a mesa structure;
An embedding portion for embedding the mesa structure portion at least from the side;
An electrode connected to the mesa structure;
Have
The embedded portion is
A first organic insulating film formed on the side of the mesa structure,
A second organic insulating film formed farther from the mesa structure than the first organic insulating film;
An inorganic insulating film formed between the first organic insulating film and the second organic insulating film;
A semiconductor device comprising:

(Appendix 2)
2. The semiconductor device according to appendix 1, wherein a part of the second organic insulating film extends to above the first organic insulating film.

(Appendix 3)
The semiconductor device according to appendix 1 or 2, wherein the electrode is in contact with an upper surface of the optical semiconductor element and an upper surface of the first organic insulating film.

(Appendix 4)
The semiconductor device according to any one of appendices 1 to 3, wherein the optical semiconductor element includes an optical waveguide.

(Appendix 5)
4. The semiconductor device according to claim 1, wherein the optical semiconductor element includes a semiconductor layer whose refractive index changes according to an electric field applied from the electrode.

(Appendix 6)
4. The semiconductor device according to any one of appendices 1 to 3, wherein the optical semiconductor element includes a semiconductor layer whose absorption coefficient changes according to an electric field applied from the electrode.

(Appendix 7)
Any one of Supplementary notes 1 to 4, wherein the inorganic insulating film has a portion that extends parallel to a side surface of the mesa structure portion and separates the first organic insulating film and the second organic insulating film. 2. A semiconductor device according to item 1.

(Appendix 8)
The semiconductor device according to any one of appendices 1 to 7, further comprising a second inorganic insulating film formed between the first organic insulating film and the mesa structure portion.

(Appendix 9)
9. The semiconductor device according to appendix 8, wherein the second inorganic insulating film extends between the first organic insulating film, the second organic insulating film, and the optical semiconductor element. .

(Appendix 10)
Forming an optical semiconductor element having a mesa structure;
Forming an embedding portion for embedding the mesa structure portion at least from the side;
Forming an electrode connected to the mesa structure;
Have
The step of forming the embedded portion includes
Forming a first organic insulating film on a side of the mesa structure;
Forming a second organic insulating film that is more distant from the mesa structure than the first organic insulating film;
Forming an inorganic insulating film between the first organic insulating film and the second organic insulating film;
A method for manufacturing a semiconductor device, comprising:

(Appendix 11)
The method of manufacturing a semiconductor device according to appendix 10, wherein a part of the second organic insulating film is extended to above the first organic insulating film.

(Appendix 12)
12. The method of manufacturing a semiconductor device according to appendix 10 or 11, wherein the electrode is formed so as to be in contact with an upper surface of the optical semiconductor element and an upper surface of the first organic insulating film.

(Appendix 13)
The method for manufacturing a semiconductor device according to any one of appendices 10 to 12, wherein the step of forming the optical semiconductor element includes a step of forming an optical waveguide.

(Appendix 14)
13. The method according to any one of appendices 10 to 12, wherein the step of forming the optical semiconductor element includes a step of forming a semiconductor layer whose refractive index changes according to an electric field applied from the electrode. A method for manufacturing a semiconductor device.

(Appendix 15)
The step of forming the optical semiconductor element includes a step of forming a semiconductor layer whose absorption coefficient changes according to the electric field applied from the electrode. A method for manufacturing a semiconductor device.

(Appendix 16)
Appendices 10 to 10, wherein the inorganic insulating film is formed so as to extend in parallel with a side surface of the mesa structure portion and to have a portion that divides the first organic insulating film and the second organic insulating film. 16. A method for manufacturing a semiconductor device according to any one of 15 above.

(Appendix 17)
17. The method for manufacturing a semiconductor device according to any one of appendices 10 to 16, wherein the inorganic insulating film is formed prior to the second organic insulating film.

(Appendix 18)
18. The method of manufacturing a semiconductor device according to any one of appendices 10 to 17, further comprising a step of forming a second inorganic insulating film between the first organic insulating film and the mesa structure portion. .

(Appendix 19)
The semiconductor device according to appendix 18, wherein the second inorganic insulating film extends between the first organic insulating film and the second organic insulating film and the optical semiconductor element. Method.

1: n-InP substrate 2: n-InP clad layer 3: i-InGaAsP core layer 4: p-InP clad layer 5: p-InGaAs contact layer 7: silicon oxide film 8: organic insulating film 10: silicon nitride film 11 : Organic insulating film 21: Mesa structure part 22: Embedding part 23: Electrode 31: Optical waveguide 32: MMI optical multiplexer 33: Electrode 34: MMI optical multiplexer 41: Demultiplexing part 42: Phase modulating part 43: Multiplexing part

Claims (6)

An optical semiconductor element having a mesa structure;
An embedding portion for embedding the mesa structure portion at least from the side;
An electrode connected to the mesa structure;
Have
The embedded portion is
A first organic insulating film formed on the side of the mesa structure,
A second organic insulating film formed farther from the mesa structure than the first organic insulating film;
An inorganic insulating film formed between the first organic insulating film and the second organic insulating film;
A semiconductor device comprising:   The semiconductor device according to claim 1, wherein a part of the second organic insulating film extends to above the first organic insulating film.   The semiconductor device according to claim 1, wherein the electrode is in contact with an upper surface of the optical semiconductor element and an upper surface of the first organic insulating film.   4. The inorganic insulating film according to claim 1, wherein the inorganic insulating film has a portion that extends in parallel with a side surface of the mesa structure and divides the first organic insulating film and the second organic insulating film. 2. The semiconductor device according to claim 1.   5. The semiconductor device according to claim 1, further comprising a second inorganic insulating film formed between the first organic insulating film and the mesa structure portion. 6. Forming an optical semiconductor element having a mesa structure;
Forming an embedding portion for embedding the mesa structure portion at least from the side;
Forming an electrode connected to the mesa structure;
Have
The step of forming the embedded portion includes
Forming a first organic insulating film on a side of the mesa structure;
Forming a second organic insulating film that is more distant from the mesa structure than the first organic insulating film;
Forming an inorganic insulating film between the first organic insulating film and the second organic insulating film;
A method for manufacturing a semiconductor device, comprising:

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